Fuel mileage on forums is like golfers saying they are shooting in the 80's- after you ask them you discover they sort of play by the rules. The numbers I posted above are real from the display in the dash. You have a couple of others posting similar numbers. Use that as your baseline not the pie in the sky numbers that seem too good to be true.

I would be wary of additional additives- these systems are nothing like a GM 5.7 diesel from the early 80's.

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Dave

'05 325xi
'10 E70 35d
'85 911 Carrera
'66 911 Work in progress
'91 Chevy C1500
'95 Jeep Cherokee
‘18 Jeep JLU